The aim of the proposed research is to determine the effects of early oxytocin (OT) or oxytocin antagonists (OTA) on the development of the hypothalamic-pituitary-adrenal (HPA) axis. Oxytocin is known to decrease the activity of the HPA axis in voles and exposure to hormones during development affects receptor distribution and number. Neonatal exposure to OT is expected to result in decreased behavioral and endocrine response to stress through decreases in corticotropin releasing hormone and its receptors and an increase in OT and OT receptors. I anticipate OTA will produce opposite effects. Furthermore, I expect consequences of OT and OTA exposure to last into adulthood. I will test these hypotheses using prairie voles (Microtus ochrogaster) as a model system. Results will have implications for human health as disregulation of the HPA axis is a risk factor for many health problems. Additionally, use of synthetic OT and OTAs to induce labor or prevent premature birth, respectively, is common. OT and OTA use in managing labor is increasing despite the fact that effects on infants are unstudied.